This invention relates to a safety device for an electrical apparatus or appliance, and more particularly to a safety device including a non-replaceable circuit interrupter.
Air moving apparatus (e.g., electric fans), appliances including a motor, or devices including electric heating elements are potentially subject to electrical problems due to accident, misuse, excessive moisture and/or heat, which can cause the wiring in a motor, the cord set, or other wires to short. Motors in appliances often incorporate a thermal cut-off device which reacts to an increase in heat to shut off the motor. Thermal devices are generally slow acting and designed to sense and react to a gradual heat increase. The heat increase can be caused by a variety of factors such as a slow acting short in the motor windings, or a bearing failure resulting in reduced air flow. Such factors may cause the winding temperature to rise.
Thermal devices are most effective at sensing localized heating, and as such, if a failure occurs at a location remote from the thermal device, the thermal device may not sense the condition quickly enough to shut the motor down prior to failure. As such, rapidly acting remote failures may result in damage to the electric device (i.e., the electrical apparatus) before the thermal device operates.
Faults that occur in appliances and electrical devices produce heat by friction, arcing, and resistive heating. The faults, and thus the sources, may occur in combination. For example, in an appliance or electrical device that utilizes an electric motor, frictional heating acts to cause bearing failure. Bearing failure acts to cause rotor lockup, and rotor lockup acts to cause inductive heating. The inductive heating breaks down insulation and causes arcing.
A properly sized circuit interrupter (e.g., a fuse) will react to rapid failure conditions and/or an increase in current over its capacity. Such a circuit interrupter will protect components upstream from the motor, such as the cord set. A circuit interrupter will also react to shorts internal to the switch, lead wires, and motor windings. A circuit interrupter, to be effective, should preferably be non-replaceable in order to insure that the user does not defeat the purpose of the circuit interrupter, which is to enhance safety of the thermal cut-off device thus preventing damage to components, the apparatus, or the appliance. In addition, the combination of these two devices (i.e., the thermal device and the circuit interrupter) in an electrical apparatus or appliance will further enhance the safety of the apparatus or appliance as well as act to protect its components.
According to an exemplary embodiment of the present invention, a safety device for use with an electric apparatus is provided. The safety device includes a housing and at least two terminals disposed at least partially within the housing. The safety device also includes a cord set having at least two conductors. A first end of the two conductors is mounted at least partially within the housing. The safety device also includes a non-replaceable circuit interrupter disposed within the housing so as to be inaccessible to a user and coupled between i) one of the at least two terminals and ii) one of the at least two conductors of the cord set.
The safety device of the present invention may be, for example, a fused cord set plug. Further, the non-replaceable circuit interrupter may be a fuse included in the cord set plug.
The present invention provides an enhanced safety device to protect an electrical apparatus or appliance from damage due to excessive heat or shorts. Further, the present invention provides an enhanced safety device that is fast and positive in operation. Further still, the present invention provides an enhanced safety device as aforesaid that is useful with a wide variety of electrical apparatus or appliances, wherein the appliances may have inductive, capacitive, or tungsten type loads. A circuit interrupter portion of the enhanced safety device can be matched to the load type by current value and trip characteristics. For example, inductive loads having in rush currents that start low may use a fast trip circuit interrupter. In contrast, tungsten and capacitive loads with higher in rush currents may be designed with a slow acting circuit interrupter.
The present invention provides a reliable and manufacturable assembly. The high injection pressures involved with molding plastic around a plug assembly can move the component parts, and potentially create an intermittent or open connection. Through certain embodiments of the present invention, component parts are encapsulated with a housing and a housing cover preventing the invasion of plastic during the molding operation. Further, the present invention provides an enhanced safety device that is no larger than devices typically found in the marketplace, although containing an additional non-replaceable circuit interrupter (e.g., fuse). This may be achieved, for example, by locating the device components in slots and cavities integral to the housing. Further still, the present invention provides an enhanced safety device as aforesaid that is reliable and relatively inexpensive to construct. Further still, the present invention provides an enhanced safety device as aforesaid that enhances the safety of the apparatus or appliance.
Other advantageous features of the invention will be apparent from the description and claims.